Polyarylate resins including bisphenol residues and aromatic dicarboxylic acid residues are well known as engineering plastics. In particular, polyarylate resins composed of bisphenol A and terephthalic acid and isophthalic acid are excellent in heat resistance, and hence are widely used as molding resins in the fields of vehicles and in the electric and electronic fields. However, the resins used in the electric and electronic fields are required to be highly flame-retardant from the viewpoint of safety, and polyarylate resin alone is insufficient in flame retardancy.
Polyarylate resins are excellent in the optical transparency in the visible ray region, and hence the application of the polyarylate resins to various optical films and various coating films to be used for, for example, liquid crystal displays has been investigated. However, unfortunately polyarylate resins are yellowed when exposed to ultraviolet ray for a long period of time, and thus the use of polyarylate resins have been restricted.
Moreover, recently in the lamination step of optical films in, for example, liquid crystal displays, ultraviolet ray curing-type adhesives have come to be used in place of conventional solvent-type adhesives from the viewpoint of the improvement of productivity or from environmental consideration. When ultraviolet ray curing-type adhesives are used, the optical films of adherends are required to transmit ultraviolet ray. Accordingly, the polyarylate resins for optical films are required to have high optical transmittance not only in the visible ray region but also in the shorter wavelength region (the ultraviolet ray region of less than 400 nm in wavelength) than the visible ray region. As such a polyarylate resins, for example, there has been used a polyarylate resin using, as the aromatic dicarboxylic acid component, diphenyl ether-4,4′-dicarboxylic acid (Patent Literature 1).